(Restatement from a comment I posted previously[0] in a related thread.)

My go-to reference is

Attachment Disturbances in Adults: Treatment for Comprehensive Repair by Daniel P. Brown PhD & David S. Elliott PhD. [1]

[0] https://news.ycombinator.com/item?id=21739622

[1] https://www.amazon.com/Attachment-Disturbances-Adults-Treatm...